The present invention relates to planetary reduction drive units, and more particularly, to such reduction drive units which include a fluid motor and are adapted for use with a vehicle wheel.
Reduction drive units of the type to which the present invention relates generally comprise a drive motor, a shaft means driven by the motor and a reduction gear train driven by the shaft means, and in turn, driving a wheel hub. Such reduction drive units are well known in the art and are exemplified by U.S. Pat. Nos. 3,686,978 and 3,737,000.
The drive unit illustrated in the cited patents has the drive motor and reduction gearing axially separated by the shaft means surrounded by a hollow spindle extending from the drive unit. Such an arrangement results in a unit which is excessive in axial length, requires a separate spindle and motor housing, in addition to the rotating hub assembly, and requires separate mountings and the like on the rotating hub and motor spindle. The illustrated arrangement effectively limits the loading to which the unit can be subjected because the bearings are disposed between the spindle and the rotating hub and are necessarily relatively small in diameter, thus limiting the available bearing capacity.
Accordingly, it is an object of the present invention to provide a reduction drive unit which is substantially shorter axially for a given torque output, and which minimizes the number of housings, mounting flanges and associated mounting means.
It is a more specific object of the present invention to provide a reduction drive unit which satisfies the above-stated objects by disposing at least a portion of the rotating hub assembly in surrounding relationship with the drive motor, and positioning the bearings between the drive motor and the rotating hub.
In the design illustrated in the cited prior patents, the main oil seal is disposed between the drive unit spindle and the rotating hub, adjacent the main bearings. Such positioning of the main oil seal makes original assembly of the drive unit more complicated and, typically, if it is necessary to remove the spindle from the rotating hub for field service, the oil seal will probably be destroyed.
Accordingly, it is an object of the present invention to provide a reduction drive unit having a main oil seal disposed between the motor housing and the rotating hub such that the drive motor and housing may be removed from the rotating hub without damage occurring to the oil seal and replacement thereof being required.
It is a more specific object of the present invention to provide a reduction drive unit which accomplishes the above-stated object by means of the drive motor housing having an external surface configured such that the drive motor may be removed from the hub with the oil seal remaining in engagement with the internal surface of the hub, and the portions of the bearing sets remaining in engagement with the motor housing passing through the inside diameter of the oil seal as the drive motor is removed.
Conventional prior art reduction drives have included a plurality of bolts passing through the cover, the rotating ring gear, and into the rotating hub, with the bolts being merely standard clearance bolts, i.e., those having a clearance of about 1/64 of an inch between the bolt and the bore. Because it is these bolts which transmit torque from the rotating ring gear to the rotating hub, the use of standard clearance bolts has permitted the possibility of failure because of stress reversals when the drive unit changes directions. In addition, it has been difficult to inspect or service the reduction gear area in prior art reduction drives, because removal of the bolts securing the cover permits the rotating ring gear to become disengaged from the hub assembly as well as the teeth of the mating planetary gears.
Accordingly, it is an object of the present invention to provide a reduction drive unit including a means for attaching the rotating ring gear and gear cover such that the cover can be removed separately without loosening the ring gear.
The cited patents illustrate several ways of disengaging the reduction gearing from the drive motor. Typically, these disengagement features involve axial shifting of the drive shaft which connects the motor shaft to the sun gear such that the drive shaft is no longer in driving engagement with the sun gear. Disengagement by axial shifting of the drive shaft generally requires a longer drive shaft including longer splined portions as well as some type of mechanism for shifting the drive shaft and maintaining it at each of the desired positions. These arrangements each require the manufacture and assembly of additional apparatus.
Accordingly, it is an object of the present invention to provide a reduction drive unit in which disengagement of the sun gear from the motor shaft may be accomplished in a simple, positive manner, without axial shifting of the drive shaft, and with no additional shifting or positioning mechanisms required.
The above and other objects of the present invention are accomplished by the provision of a reduction drive unit in which the rotating hub assembly includes a wheel mounting flange, a first hub portion and a second hub portion extending from the wheel mounting flange toward the inboard end of the unit, oppositely disposed from the first hub portion. The drive motor includes a motor housing disposed within the second hub portion, the motor housing defining a generally cylindrical external surface and the hub portion defining a generally cylindrical internal surface. A bearing means and an oil seal are disposed between the internal surface and the external surface, the oil seal being disposed between the bearing means and the inboard end of the unit.
In accordance with a more limited aspect of the present invention, the external surface includes first and second external portions and the internal surface includes first and second internal portions, the second portions being disposed between the first portions and the inboard end. The bearing means is disposed between the first internal portion and the first external portion and the oil seal is disposed between the second internal portion and the second external portion, the second external portion having a diameter sufficiently larger than the diameter of the first external portion to permit removal of the motor housing from within the second hub portion and passage of the inner race of the bearing means through the oil seal without damage thereto.
In accordance with another aspect of the present invention, the first hub portion and rotating ring gear define a first plurality of bores and the first hub portion, rotating ring gear and cover member define a second plurality of bores. A first plurality of bolts threadedly engage the first plurality of bores and the second plurality of bolts threadedly engage the second plurality of bores to permit removal of the cover member from the drive unit without loosening the ring gear. Preferably, the first and second pluralities of bolts are arranged in a circumferentially alternating pattern.
In accordance with still another aspect of the present invention, the drive shaft connected to the motor shaft and driving the sun gear has first and second axially disposed end portions, the first portion including means engaging the sun gear and the motor shaft to substantially prevent relative rotation therebetween when the drive shaft is in a first orientation with the first end portion adjacent the motor shaft. The second end portion is configured to extend through the sun gear to permit free, relative rotation between the motor shaft and the sun gear when the drive shaft is in a second orientation with the second end portion adjacent the motor shaft.